This invention relates to hydraulically operated tools, and more particularly to a hand-held forcing tool of the type having thereon a telescopic forcing rod which can be utilized for forcing or prying open doors, such as for example automobile or building doors which are jammed or locked closed.
It is often necessary for firemen or police officers, for example, to utilize some form of tool for prying or forcing open closed doors which have been locked or jammed into closed positions, such as for example as the result of an automobile accident, or in the course of attempting to enter a burning building or the like. Among the most fundamental tools for use in opening such doors is a conventional crow bar or pinch bar. However, in order to be able to exert even greater pressure, tools have been developed which utilize a hydraulic mechanism for gaining forced entry to a car, building, or the like. One such tool, by way of example, is disclosed in U.S. Pat. No. 5,251,445.
The tool disclosed in the above-noted patent utilizes a hydraulically operated forcing rod, which telescopes into and out of a hydraulic cylinder housing. A hand-operated pump, which is attached to the housing, can be manipulated to cause fluid under pressure to force the telescopic rod out of the housing against the resistance of a spring. When it is desired to retract the rod back into the housing, a lever is operated manually in order to release the hydraulic pressure and to permit the spring to retract the forcing rod back into the housing.
One of the major disadvantages of a tool of the type described, and in particular the tool disclosed in the above-noted U.S. Pat. No. 5,251,445, is that the apparatus which is utilized for maintaining pressure on the reservoir that supplies hydraulic fluid to an associated pumping device, is very expensive to manufacture, and difficult to repair. More specifically, such a mechanism utilizes a tubular forcing rod having intermediate its ends an integral partition, one side of which is attached to one end of a tension spring which is utilized to retract the forcing rod from its extended to its retracted position. The opposite side of the partition opens on one end of a fluid reservoir, the opposite end of which comprises a spring-loaded piston that reciprocates in the forward end of the forcing rod in response to changes in the pressure of the fluid which is maintained in the reservoir.
It is very difficult and time consuming to provide in the forward end of the forcing rod an elongate bore for slidably accomodating the spring loaded piston which is employed to exert pressure on the fluid in the reservoir. Also, of course, the piston must be mounted so as to prevent fluid from seeping past the piston from one end of the bore in the rod to the other end. If repairs are necessary, the entire front end of the forcing rod must be removed to gain access to the piston.
It is an object of this invention, therefore, to provide a simplified hydraulically operated tool of the type described which obviates the need for employing a spring-loaded piston within the bore of the forcing rod in order to maintain pressure on the fluid in the reservoir.
A more specific object of this invention is to provide an improved tool of the type described which utilizes novel fluid pressure generating means which are mounted on the exterior of the associated hydraulic cylinder housing rather than within the tool's forcing rod, thus considerably reducing the cost of manufacturing, and of maintaining satisfactory operation of such tool.
Other objects of the invention will be apparent hereinafter from the specification and from the recital of the appended claims, particularly when read in conjunction with the accompanying drawings.